WASHINGTON — Senior U.S. officials repeatedly pleaded with senators to support a measure authorizing President Obama to attack Syria, arguing it is not a vote to declare war.

Secretary of State John Kerry told the Senate Foreign Relations Committee that Obama is not asking “to go to war” with Syrian President Bashar al-Assad and his forces. Rather, Obama is asking for the authorization to launch “limited strikes” to show “the U.S. means what it says.”

The latter part of that statement is a reference to Obama’s August 2012 declaration that if Assad used chemical weapons on Syrian civilians or citizens, that would constitute a “red line” that would change the American president’s calculus for deciding whether to green-light cruise missile strikes on Assad’s chemical arsenal.

In a poignant moment, Sen. John McCain, R-Ariz., asked whether the Pentagon had been asked to examine military options that would flip momentum in Syria’s civil war toward opposition forces.

“I have never been told to change the momentum,” Dempsey said. “I have been told to deter and degrade.”

Committee Chairman Robert Menendez, D-N.J., who is leading the effort to revamp the use-of-force resolution the White House sent Congress on Saturday to address senators’ myriad concerns.

“What is before us is a request, and I quote, ‘to prevent or deter the use or proliferation of chemical or biological weapons within, to, or from Syria’ and ‘to protect the United States and its allies and partners against the threat posed by such weapons,’” he said, reading from the White House document.

“This is not a declaration of war but a declaration of our values to the world,” Menendez said. “A declaration that says we are willing to use our military power when necessary against anyone who dares turn such heinous weapons on innocent civilians anywhere in the world.”

McCain wants a military mission strong enough to give opposition forces the upper hand or even force out Assad. And he has faulted the White House for moving too slowly and inadequately in aiding rebel forces.

But on Tuesday he said a congressional rejection of a use-of-force resolution would send “a bad message” not only to Assad, but across the region.

Kerry, the most forceful of the three Obama administration witnesses appearing before the panel, said striking Syria is important to send a message about using the world’s most deadly weapons — not only to Assad but to leaders in Iran and North Korea: “Never means never.”

Kerry, the last Senate Foreign Relations Committee chairman, warned senators “if we don’t respond, we’re going to be back here” asking Congress to approve an even bigger military mission spawned by another rogue world leader “miscalculating” America’s will to act.

The administration’s witnesses — Defense Secretary Chuck Hagel also testified — time and again stressed the White House-crafted resolution is focused solely on Assad’s chemical weapons.

Senators from both parties voiced skepticism about launching military operations in another Middle East nation. Some alluded to what many experts, officials and lawmakers now see as America’s misadventure in Iraq.

Sen. Richard Durbin, the chamber’s No. 2 Democrat, pressed hard on questions about a congressional authorization leading to a bigger U.S. mission than just missile strikes. In return, he received Kerry’s “word” that it would not.

Some of the hearing’s most memorable moments stemmed from Kerry, under questioning, initially saying he would not rule out the need for U.S. boots on the ground inside Syria.

The flap caused Kerry to at several points to later address his “thinking out loud.”

“All I did was raise a hypothetical question about some possibility — and I’m thinking out loud — about how to protect America’s interests.”

“There will not be American boots on the ground ...” Kerry said — but he then added this caveat: “... with respect to the Syrian civil war.”

Kerry seemed open to a resolution that would include language addressing lawmakers’ concerns about US boots on the ground, and limiting the operation’s duration.

Even after clarifying his comment several times, America’s top diplomat was still taking fire — serious and tongue-in-cheek — on social media sites like Twitter.

Democratic members of the 18-senator panel voiced their full-throated or tepid support for the White House’s plan to strike Syria’s chemical weapons arsenal.

Sen. Barbara Boxer, D-Calif., warned if the U.S. does not strike, Iran might view Washington “as a paper tiger.” That could lead Tehran to attack Israel, Boxer said.

Boxer also said North Korea also might get more aggressive if the U.S. stands aside on Syria.

While several Republican members criticized the Obama administration’s plans and its past actions — or lack thereof — on Syria, Sen. Marco Rubio, R-Fla., appeared to join the McCain camp.

Rubio broke with Sen. Rand Paul, R-Ky., a potential 2016 presidential nomination rival, by saying what happens in Syria matters to the United States.

Rubio warned U.S. inaction could embolden Iran and North Korea, and even spawn a nuclear arms race across the Middle East and North Africa. He wants a war plan that would be tailors to “tip his calculation” toward fighting the rebels instead of again using chemical arms, referring to Assad.

He and Kerry dueled for several minutes over what the senator sees as a confusing disconnect before the secretary of state finally asked whether Johnson believes Congress would be willing to approve a regime-change operation. His implication was clear: It is not. Johnson did not directly address the witness’s rhetorical question.

Johnson and other Republicans asked if the kind of “limited” mission envisioned by the White House would tip the balance toward the rebels.

The witnesses said “degrading” Assad’s chemical weapons arsenal would limit the Syrian leader’s military options, thereby weakening his hand in the nation’s civil war.

White House officials will brief the panel in closed session on Wednesday.

Menendez, has been working with Sen. Bob Corker, R-Tenn., the panel’s ranking member, to revise the White House-crafted resolution. Menendez said there is a “possibility” the full committee could mark up a revised version of the use-of-force measure as early as Wednesday.

The House will hear from the administration witnesses on Wednesday. The administration’s resolution is expected to be a harder sell in the GOP-controlled House than the Democratic-controlled Senate.

If the chambers’ versions are different, and both pass, a conference committee would have to hammer out any differences.

Sen. Paul said it is “unlikely” that lawmakers will vote down Obama’s desired use-of-force resolution.

Paul said he “was proud [Obama] was my president” when he heard about the president’s Saturday announcement that he would seek congressional approval before deciding whether to launch Tomahawk missiles.

But he expressed disappointment that Obama signaled in the same Saturday speech that even if Congress defeats a force resolution “I’ll probably do the bombing anyway.”

The libertarian GOP senator told the witnesses that if one or both chambers defeat the Syria resolution and Obama attacks anyway: “You’ll be making a joke out of us.”